Method of Machining Fibre Board

ABSTRACT

What is disclosed is a method of machining a fibreboard, wherein the fibreboard, which may have a non-uniform content of moisture, is cut into at least two fibreboard sections. The fibreboard sections are then provided with complementary matching orientation determining joining means along their lateral edges. A first type of orientation determining joining means is provided on a relatively dry lateral edge of a first fibreboard section, while a second type of orientation determining joining means is provided on a relatively moist lateral edge of a second fibreboard section.

This invention regards a method of machining fibreboards. Moreparticularly, it regards a method of machining fibreboards in which onesection of the fibreboard is turned around after the board has been cutinto at least two sections, for subsequent machining, e.g. milling of atongue and groove along the longitudinal lateral edges of the boardsections. The method is particularly appropriate for the machining ofpanel boards that, when mounted; cover a surface in a room.

When machining fibreboards, which are often decorated on one side, it iscommon, for production related reasons, to produce relatively largeboards that are typically cut into two equally sized board halves in thecourse of the subsequent machining.

After cutting, the board halves are moved through a machine in which agroove and a tongue, respectively, are milled into at least two oppositelateral edges of each board half.

In prior art, a fibreboard is often cut longitudinally, whereupon afirst board half is first transported to a machine for milling of atongue and groove, whereupon, following a lateral displacement, thesecond board half follows the first board half to the same machine.

With this method of machining, the groove of e.g. the first board halfwill be on the side of the first board half that formed the outside edgeof the original full board, while the tongue of the first board halfwill be on the side of the first board half that, prior to halving, wascontiguous to the second board half.

Likewise, the groove of the second board half will be on the side of thesecond board half that, prior to halving, was adjacent to the firstboard half, while the tongue of the second board half will be on theside of the second board half that formed the outer lateral edge of theoriginal full fibreboard.

Thus when mounted, after joining the tongue and groove, the fibreboardsare assembled as they were in the original full fibreboard.

It has proven difficult to achieve a uniform content of moisture in afibreboard. Typically the moisture content is higher in the middlesection of a fibreboard than along its lateral edges. A certainequalizing of this moisture content must be expected after thefibreboard has been mounted. A reduction in moisture causesshrinkage/contraction, and it is known for fibreboard halves to pullapart slightly as they dry out. People in the trade know this phenomenonas “curving”. The problem is made worse by board halves producedaccording to prior art drawing in opposite directions after beingmounted. Exaggerating a little, one may say that the fibreboard halvesform arches with paired concave and convex, respectively, sides facingeach other.

The object of the invention is to remedy or reduce at least one of thedrawbacks of prior art.

The object is achieved in accordance with the invention, by the featuresspecified in the description below and in the following Claims.

According to the invention this problem of shrinkage is solved byallowing the fibreboards on e.g. a wall to contract in the samedirection. Thus the concave side of a fibreboard section is mounted tothe convex side of an adjacent fibreboard section. Typically thesefibreboard sections constitute a fibreboard half.

The method means that the groove of each fibreboard section must belocated on the side of the original fibreboard which formed the outsidelateral edge, alternatively on the side of the one fibreboard sectionthat was located adjacent to the second fibreboard section, and that thetongue of the fibreboard section must be on the opposite side.

By so doing the groove of one fibreboard section will be milled in arelatively dry area of the fibreboard section, and it will be coupled toa tongue milled in a relatively moist area of the other fibreboardsection.

When the fibreboards dry they will draw in the same direction, thusachieving approximately the same curvature. Thus the fibreboard sectionswill pull apart only slightly.

When machining a fibreboard where the fibreboard, which may have anon-uniform moisture content, is cut into at least two fibreboardsections, and where the fibreboard is then provided with complementaryorientation determining means of joining along at least two of itslateral edges, a first type of orientation determining joining means isprovided on a relatively dry lateral edge, while a second type oforientation determining joining means is provided on a relatively moistlateral edge.

The term orientation determining joining means implies a joining meansthat prevents the fibreboard sections from being assembled in just anyorientation relative each other.

The method is implemented quite simply by at least one of the fibreboardsections being turned around prior to being provided with orientationdetermining joining means.

A typical orientation determining joining means is a tongue and a grooveon opposite lateral edges.

In what follows is described a non-limiting exemplary embodiment of apreferred embodiment illustrated in the accompanying drawings, in which:

FIG. 1 is a principle drawing of a mounting of fibreboard halvesproduced according to prior art, where the curving due to dehydration isgreatly exaggerated;

FIG. 2 is a principle drawing of a mounting of fibreboard halvesproduced according to the invention, where the curving due todehydration is greatly exaggerated;

FIG. 3 is a principle drawing on a slightly smaller scale, showing afibreboard being cut into two fibreboard halves;

FIG. 4 is a principle drawing showing the fibreboard of FIG. 3 aftercutting, where a first fibreboard half is being transported tosubsequent machining, while a second fibreboard half is being rotatedthrough 180 degrees in the plane of the board;

FIG. 5 shows the second fibreboard half, after having been rotatedthrough 180 degrees, as it follows the first fibreboard half to thesubsequent machining; and

FIG. 6 is an end view of the fibreboard halves, on a larger scale.

In the drawings, reference number 1 denotes a clean-cut fibreboard witha middle section 2, a first longitudinal lateral edge 4, a secondlongitudinal lateral edge 6, a first transverse edge 8 and a secondtransverse edge 10, see FIG. 3.

The moisture content of the fibreboard 1 is higher in the middle section2 than at the outer edges 4, 6, 8 and 10. After the fibreboard has beencut longitudinally into a first fibreboard half 12 and a secondfibreboard half 14 by e.g. a saw blade 16, the first fibreboard halfcomprises the first longitudinal lateral edge 4 and an opposite thirdlongitudinal lateral edge 18. The second fibreboard half 14 comprisesthe second longitudinal lateral edge 6 and an opposite fourthlongitudinal lateral edge 20. The third longitudinal lateral edge 18 andthe fourth longitudinal lateral edge 20 were created when the fibreboard1 was cut through the middle section 2 of the fibreboard 1.

It is to be expected that the fibreboard halves 12 and 14 will contractmore along their respective third and fourth longitudinal lateral edges18, 20 than along their respective first and second longitudinal lateraledges 4, 6.

After the splitting, the first fibreboard half 12 is movedlongitudinally to a following machine in which the first fibreboard half12 receives a groove 22 in its relatively moist third longitudinallateral edge 18 and a tongue 24 in its relatively dry first longitudinallateral edge 4, in a manner that is known per se.

The tongue 24 and groove 22 constitute a first type of orientationdetermining joining means and a second type of orientation determiningjoining means, respectively.

The second fibreboard half 14 is then rotated through 180 degrees in theplane of the board, and so is turned around before following the firstfibreboard half 12 to the machine (not shown).

The second fibreboard half 14 receives a groove 22 in its relativelymoist fourth lateral edge 20 and a tongue 24 in its relatively drysecond lateral edge 6, in the same way as the first fibreboard half 12.

Thus upon mounting, see FIG. 2, the relatively moist third longitudinallateral edge 18 of the first fibreboard half 12, with the groove 22, isa complementary match to the relatively dry second longitudinal lateraledge 6 of the second fibreboard half 14, which edge is provided with atongue 24. Likewise, the relatively moist fourth longitudinal lateraledge 20 of the second fibreboard half is a complementary match to therelatively dry first longitudinal lateral edge 4 of another firstfibreboard half 12 etc.

When the moisture content of the fibreboard halves 12, 14 evens outafter mounting, the fibreboard halves 12, 14 will draw in the samedirection, thereby preventing cracks from occurring between therespective longitudinal lateral edges 4, 6, 18 and 20.

1: A method comprising: splitting a fibreboard into at least twofibreboard sections; forming a complementary joining means along therelatively dry lateral edge of a first fibreboard section; and forming acomplementary joining means along the relatively moist lateral edge of asecond fibreboard section. 2: The method of claim 1, wherein at leastone fibreboard section is laterally rotated 180 degrees prior to theforming step. 3: The method of claim 1, wherein at least one fibreboardsection is axially rotated 180 degrees prior to the forming step. 4: Themethod of claim 1, wherein the orientation determining joining means isa tongue. 5: The method of claim 1, wherein the orientation determiningjoining means is a groove.